论文详情
发育定向排列垂直裂缝的油气储层可以等效为具有水平对称轴的横向各向同性(HTI)介质, 裂缝的发育程度可以用裂缝弱度参数来刻画。在贝叶斯理论的框架下, 利用方位地震振幅差异, 提出了一种基于各向异性梯度的裂缝弱度AVAZ反演方法。首先, 基于线性滑动模型理论求取干裂缝的法向与切向弱度之间的相关性, 推导了各向异性梯度与裂缝弱度的关系式。其次, 利用叠前地震数据提取HTI介质AVO各向异性梯度属性, 构建了裂缝弱度参数的初始模型, 为后续裂缝参数反演提供更加准确的先验约束信息。为了提高储层的裂缝预测精度, 利用方位地震数据振幅差异, 消除了背景介质的干扰。最后, 开展基于贝叶斯理论的AVAZ叠前反演, 实现了HTI介质储层裂缝弱度的估算。该方法的优势在于能够获得较为准确的初始模型, 突出裂缝参数在反演过程中的贡献。模型和实际地震数据的应用结果与测井解释结果以及地质认识吻合较好, 表明该方法具有良好的稳定性与可行性, 是一种可靠的裂缝型储层预测方法。
Reservoirs with vertically oriented fractures are equivalent to transversely isotropic media with a horizontal symmetry axis (HTI), and fractures could be characterized using fracture weakness.Under the Bayesian framework, an AVAZ inversion method based on anisotropic gradient is developed to calculate fracture weakness using azimuthal amplitude difference.Dry fracture weakness correlation is derived from the linear sliding model.Based on the relationship between anisotropic gradient and fracture weakness, AVO anisotropic gradient extracted from prestack seismic data is used to establish the initial model of fracture weakness, which functions as prior information constraints for inversion.Prestack AVAZ inversion is implemented to estimate fracture weakness of HTI media based on the Bayesian theory.To improve fracture prediction, azimuthal amplitude difference is used to mitigate the interference of background media.Owing to the accurate initial model and increasing influence of fracture parameters in the inversion, model data and field data tests show good results consistent with log interpretation and geologic knowledge, which demonstrates the robustness and credibility of the method.